1. Field of the Invention
The invention relates to methods for the determination of materials deposited on surfaces. Many areas of industry are in need of a reliable, rapid method to employ to detect surfactants. Many surfactants are used on metal surfaces for cleaning, and the complete removal of these cleaning surfactants must be checked prior to painting or further conditioning the surface. In the medical arts, hospitals check for the complete removal of cleaning surfactant on paperware, glassware and dishes which the patients use to insure purity of foods and drugs dispensed. Similarly, the cosmetic industry uses some surfactants in cosmetic preparations and the type and amount of these surfactants are needed to be followed for quality control. Particularly, the invention relates to a method for determining the presence on surfaces of surfactants, such as linear alkyl sulfonates, alkylarylsulfinates, linear long-chain carboxylic acids, such as oleic acid and its salts, and synthetic polymeric surfactants, such as polyoxyethylenestearates. The invention relates specifically to the detection and quantification of such surfactants on surfaces including nonionic and ionic surfactants which have been deposited on the exterior surfaces of glass articles, particularly glass bottles and jars.
In the glass processing art, glass articles, bottles for example, are usually delivered to further processing stations after their formation to be packaged, polished, filled, or the like. As the glass articles are moved from one station to another, they frequently contact each other. This contact may result in abrasion on the surfaces of the glass which not only lessens the aesthetic value of the glass, but may also diminish the structural integrity of the glass.
To lessen the abrasion of the glass from these contacts, techniques have been developed to spray or otherwise coat a uniform layer of suitable surfactants onto the glass surfaces. When the coated glass articles contact each other, the tendency is for them to move against each other as frictionlessly as possible so as not to scratch or mar their surfaces.
Glass articles coated with surfactant are usually stored for long periods of time before their use. Uncoated articles may also be stored for long periods of time. When either coated or uncoated articles are returned for filling, labeling, etc., after having been stored for weeks or even months, it is difficult to know if a particular batch or lot of glassware has been treated or not treated with surfactant.
It is, therefore, desirable to have a method to detect if there is, in fact, a surfactant on the surface. Unfortunately, the surfactant coating is so thin that it is impossible to detect the presence by visual observation, and if present, in approximately what surface concentration. The method must be functional even in the areas of the production facilities like warehouses and loading docks, so that bottles and the like can be tested on-site and do not have to be removed to a laboratory for analysis. Additionally, the test should be simple, so that the average line worker may use the test without substantial training or expertise. Also, the test must be inexpensive and usable on a routine basis for on-line quality control in large-scale operations, as well as post-processing detection of surfactant.